RE: [PATCH v9 2/4] gadget: Support for the usb charger framework

[Jun Li]

> -----Original Message-----
> From: Felipe Balbi [mailto:balbi@xxxxxxxxxx]
> Sent: Wednesday, April 06, 2016 8:22 PM
> To: Jun Li <jun.li@xxxxxxx>; Baolin Wang <baolin.wang@xxxxxxxxxx>; Peter
> Chen <hzpeterchen@xxxxxxxxx>
> Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>; Sebastian Reichel
> <sre@xxxxxxxxxx>; Dmitry Eremin-Solenikov <dbaryshkov@xxxxxxxxx>; David
> Woodhouse <dwmw2@xxxxxxxxxxxxx>; Peter Chen <peter.chen@xxxxxxxxxxxxx>;
> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>; r.baldyga@xxxxxxxxxxx; Yoshihiro
> Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>; Lee Jones
> <lee.jones@xxxxxxxxxx>; Mark Brown <broonie@xxxxxxxxxx>; Charles Keepax
> <ckeepax@xxxxxxxxxxxxxxxxxxxxxxxxxxx>; patches@xxxxxxxxxxxxxxxxxxxxxxxxxxx;
> Linux PM list <linux-pm@xxxxxxxxxxxxxxx>; USB <linux-usb@xxxxxxxxxxxxxxx>;
> device-mainlining@xxxxxxxxxxxxxxxxxxxxxxxxx; LKML <linux-
> kernel@xxxxxxxxxxxxxxx>
> Subject: RE: [PATCH v9 2/4] gadget: Support for the usb charger framework
> 
> 
> Hi,
> 
> Jun Li <jun.li@xxxxxxx> writes:
> >> -----Original Message-----
> >> From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-
> >> owner@xxxxxxxxxxxxxxx] On Behalf Of Baolin Wang
> >> Sent: Wednesday, April 06, 2016 6:47 PM
> >> To: Peter Chen <hzpeterchen@xxxxxxxxx>
> >> Cc: Felipe Balbi <balbi@xxxxxxxxxx>; Greg KH
> >> <gregkh@xxxxxxxxxxxxxxxxxxx>; Sebastian Reichel <sre@xxxxxxxxxx>;
> >> Dmitry Eremin-Solenikov <dbaryshkov@xxxxxxxxx>; David Woodhouse
> >> <dwmw2@xxxxxxxxxxxxx>; Peter Chen <peter.chen@xxxxxxxxxxxxx>; Alan
> >> Stern <stern@xxxxxxxxxxxxxxxxxxx>; r.baldyga@xxxxxxxxxxx; Yoshihiro
> >> Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>; Lee Jones
> >> <lee.jones@xxxxxxxxxx>; Mark Brown <broonie@xxxxxxxxxx>; Charles
> >> Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxxxxxxxx>;
> >> patches@xxxxxxxxxxxxxxxxxxxxxxxxxxx;
> >> Linux PM list <linux-pm@xxxxxxxxxxxxxxx>; USB
> >> <linux-usb@xxxxxxxxxxxxxxx>;
> >> device-mainlining@xxxxxxxxxxxxxxxxxxxxxxxxx; LKML <linux-
> >> kernel@xxxxxxxxxxxxxxx>
> >> Subject: Re: [PATCH v9 2/4] gadget: Support for the usb charger
> >> framework
> >>
> >> On 6 April 2016 at 15:19, Peter Chen <hzpeterchen@xxxxxxxxx> wrote:
> >> > On Fri, Apr 01, 2016 at 03:21:50PM +0800, Baolin Wang wrote:
> >> >>
> >> >> @@ -563,6 +564,8 @@ struct usb_gadget_ops {
> >> >>       struct usb_ep *(*match_ep)(struct usb_gadget *,
> >> >>                       struct usb_endpoint_descriptor *,
> >> >>                       struct usb_ss_ep_comp_descriptor *);
> >> >> +     /* get the charger type */
> >> >> +     enum usb_charger_type (*get_charger_type)(struct usb_gadget
> >> >> + *);
> >> >>  };
> >> >
> >> > Since we already have get_charger_type callback at usb_charger
> >> > structure, why we still need this API at usb_gadget_ops?
> >>
> >> In case some users want to get charger type at gadget level.
> >>
> > Why gadget needs to know charger type? I also don't catch the intent
> > of
> 
> because some gadgets need to call usb_gadget_vbus_draw(), although for
> that they need power in mA rather.

In below change of usb_gadget_vbus_draw(), already can get charger type
via usb_charger_get_type().

static inline int usb_gadget_vbus_draw(struct usb_gadget *gadget, unsigned mA)
 {
+       enum usb_charger_type type;
+
+       if (gadget->charger) {
+               type = usb_charger_get_type(gadget->charger);
+               usb_charger_set_cur_limit_by_type(gadget->charger, type, mA);
+       }
+
        if (!gadget->ops->vbus_draw)
                return -EOPNOTSUPP;
        return gadget->ops->vbus_draw(gadget, mA);

Could you detail in what situation gadget->ops-> get_charger_type() is used?

> 
> > This api, as my understanding, gadget only need report gadget state
> changes.
> > All information required for usb charger is charger type and gadget
> state.
> 
> you're making an assumption about how the HW is laid out which might not
> be true.
> 

What other information you refer to here? Or what I am not aware of?

Thanks.
Li Jun  

> --
> balbi